Next, let's get our air cylinder together. Be sure to use teflon plumber's tape on all the threads of the fittings and make sure all of your connections are very tight, as this will be under high pressure. Attach the end cap to one end of the pipe and the reducer to the other. Then once you assemble the two close 1" threaded fittings to each end of the T fitting, install the air nipple and 1/4" to 1/2" reducer to the right angle of the same. Screw this in tight to the 2" to 1" reducer as seen here. Now it is a matter of screwing the sprinkler valve down to this assembly as shown here just prior to installing the expansion chamber to the exhaust.

   Now we will need a way to trigger our valve and here is one way to achieve this. Of course you could easily hook up a couple of 9 volt batteries to the valve and that would certainly work, but I like the convenience of 110V myself, so I went to the thrift store and picked up a 12 volt transformer for .60 cents and lopped off the power cord. I attached these two wires to the ones coming out of the cap of the valve with two crimp fittings shown in this photo on the left. If you look very closely at the two prongs on the transformer you can see I have shortened them with my die grinder, and I also trimmed them slightly smaller so my 1/4" female quick slide electrical fittings would slip right on to them. I then clipped off the female end of my extension cord and attached the two connectors as shown on your right to each one and plugged them into the transformer. I simply used heat shrink tube to cover both of the legs and zip-tied the cords to the throat of the cannon. Then I used two heavy zip ties to attach the transformer to the side of the T fitting as shown here. If you look close you can see I used two more smaller ties, one on each side to keep the first ones from sliding off. This makes my cannon fully contained, and easy to transport.

   The amount of ON time that the cannon requires is obviously very very short, like 1/10th of a second or so. Due to this I realize that trigging really needs to be an actor-controlled thing, rather than automating. For ease of use and flexibility I tried using a wireless remote control unit used for light switches, but found that there is a complication with triggering an electric transformer this way and it would not work. For some reason the transformer is supplied a trickle of power even when the remote is not being activated, so the valve stays slightly open. So a really simple fix (and really CHEAP at $2 each) I found for this is to mount a power strip close enough to the cannon to plug it in, and use the reset switch as an on and off trigger. This worked great all night last Halloween at the charity haunt I was working at where we were using 4 cannons throughout the evening. And these were highly effective startle props! We used ours at 60 PSI and the concussion was very heavy. I doubt you would want to run them at any higher pressure, as it may actually be dangerously too loud!

   Next we add a little safety to our little noise maker.